1. Field of the Invention
This invention relates to a scaffolding system comprising a plurality of step-shaped supports wherein the down leg of each support bears against a wall, the upright leg adapted to receive a safety rail and a walkway support comprising a flat between the legs, each step-shaped support supported above the working surface and against the wall with an outrigger fixed to the apex between the down leg and the walkway support. A guard rail is pinned to each upright leg thus becoming an integral structural part of the scaffolding system. The scaffolding system may also be made freestanding by clamping together the down legs of two step-shaped supports in opposed relationship using the outrigger to establish a tripod sub-assembly. Thereafter, two sub-assemblies are spaced apart and joined by walk boards or stages placed upon the walkway supports.
2. Prior Art Statement
It is known to provide a scaffold for a building comprising brackets and shore timbers wherein the brackets are raised and lowered with facility by pinning the foot of the shore timbers nearer or further from the wall. For instance, see the U.S. Pat. No. 73,346 issued on 14 Jan. 1868, to Lamb and Livings. It is further known to hold a bracket against a building wall with a joist or studding. For instance, see the U.S. Pat. No. 834,919 issued on 6 Nov. 1906 to Frank Mackie. Also, it is known to construct a scaffold with two or more brackets resting against an upright wall with a prop embedded in and resting upon the ground or floor wherein the prop is retained against the bracket by a pin through a triangular plate. See the U.S. Pat. No. 1,347,453 issued on 20 Jul. 1920, to Karl Gamer. Additionally, known is the MonoJack System manufactured by ReechCraft wherein individual brackets are supported against a wall by a telescoping leg section. The Mackie scaffold must be anchored to the wall. In all of the above scaffolds, each bracket is independently supported against the wall without structural relationship to any other bracket. Furthermore, no safety rails are provided between the brackets nor is provision made for adding safety rails. The individual brackets and braces, when subjected to side loads, tend to slide along the wall causing failure of the scaffold.
It is also known to provide a pair of standards arranged in an upwardly converging direction positioned below an horizontally disposed timber supporting member wherein one end of the timber supporting member is pivotally connected to the apex of the upwardly converging members and while the other end has a foot thereon which rests against the wall. For instance, see the U.S. Pat. No. 2,966,957 issued on 3 Jan. 1961 to Herbert Ireland or the U.S. Patent Publication 2002/0178683 A1, published on 5 Dec. 2002 by Robert M. Phillips. No safety rail is provided nor is provision made to add a safety rail. Additionally, the standards are adapted to use planking laid upon the horizontal leg and are not suitable for use with modern walkboards.
It is further known to provide an adjustable bracing system for bracing of insulated concrete walls during the construction thereof, the system comprising a substantially vertical brace, an adjustable length angled leg member, a scaffolding framework extending substantially horizontally and mounted along a first edge of the brace wherein the angled leg member is fixed to the vertical brace. For instance, see U.S. Pat. No. 5,388,663 issued on 14 Feb. 1995 to Phillippe, et al., U.S. Pat. No. 6,065,254 issued on 23 May 2000 to Richard Lanka, the U.S. Pat. No. 6,247,273 issued on 19 Jun. 2001 to Shane Nickel, the PanelJack offered for sale by ReechCraft, the U.S. Pat. No. 6,446,752 issued on 10 Sep. 2002 to Michel Philippe and the U.S. Publication 2002/0073634 A1 issued on 20 Jun. 2002 by Bolinger, et al. The scaffolding systems described in Phillippe, et al., and Bolinger, et al., must be anchored to the wall with straps surrounding the legs of the scaffolding brackets. Although most of these patents have provisions for adding a safety rail having a standard loosely placed in a socket at the end of the walkway support, the safety rail is not structurally sound nor does the safety rail provide structural support to the scaffolding system. Furthermore, these bracing systems are suitable for standard planking laid upon the horizontal members and generally do not accept modern walkboards which positively engage each horizontal member.
It is known to provide a free standing, square rigged scaffolding system comprising at least two substantially square end members joined together with cross braces preferably on both side edges to lend rigidity to the scaffolding system. Planking is then laid upon the crossbars of the end members wherein the worker walks upon the walk boards while working in the elevated position. The square rigged scaffold is difficult to erect and must be placed on a substantially level surface as there is limited adjustment to the height of each leg. Square rigged scaffolding may only be extended upwardly by building additional end members upon the tops of the next lower end member by the worker working in an elevated position. Furthermore, no safety rails have been provided for square rigged scaffolds nor is provision made for safety rails. The time required to erect square rigged scaffolding would not permit rapid deployment of repair crews in an hostile environment. For instance, see the U.S. Pat. No. 2,481,885 issued on Sep. 13, 1949 to Eugene H. Simpson.
Provisions have been made to lock pre-made staging to square rigged, free standing scaffolding by providing a hook like portion on the end of the walkway with a locking element associated therewith. For instance, see the U.S. Pat. No. 2,997,767 issued on Aug. 29, 1961 to Grover, et al., or the U.S. Pat. No. 6,530,456 B1 issued on Mar. 11, 2003 to Harry Wallther. The staging described in these patents requires manipulation of a latch on both ends of the staging in order to secure same to the scaffold.
A safety improvement on pre-made staging for a square rigged scaffold system comprises a guard post and means for coupling the post to pre-made staging is shown in U.S. Pat. No. 4,984,654 issued on Jan. 15, 1991 to Carl Anderson. As the guard posts are fixed only to the staging, no additional structural integrity is provided to the scaffolding system as impact against the guard post or any associated guard rail would tip the pre-made staging along with the safety rail possibly resulting in injury to the worker.
A tripod joint has been proposed for a tripod step ladder which comprises a C-shaped link to join together the legs of the tripod while allowing the tripod to be collapsed for ease of transport. The link binds the splayed legs of the tripod against the ladder leg. For instance, see the U.S. Pat. No. 4,524,849 issued on Jun. 25, 1985 to Ronald Riddle. Though not discussed or shown by the inventor, the tripod system might conceivably be used as ends of a scaffolding system by placing planking upon the steps of the opposed ladders, the height of such a ladder/scaffold is limited to the length of the ladder. No safety rails or other safety measures have been provided for retaining the worker upon the ladder/scaffold.
A tripod ladder is described in U.S. Pat. No. 5,685,391 issued on Nov. 11, 1997 to James Gundlach, the tripod consisting of at least one extendible ladder joined to two other legs with a triangular member. In practice, the triangular member may only be affixed to the top most rung on the ladder with the other two legs splayed outwardly on a flat surface at 120 degrees which requires considerable space to assemble the ladder. Most construction locations have limited space to erect elevated platforms and the tripod ladder of this invention would not allow erection in a limited space. Furthermore, no scaffolding is contemplated by the inventor nor would it be practical to use the tripod so described as so much erection space is required.
Finally, it is known to provide free standing towers for a scaffolding system as shown in U.S. Pat. No. 4,641,728 issued on Feb. 10, 1987. Each tower comprises an upstanding mast and a three-legged base. One leg of the base is fixed to the mast while the other two legs are swingable adjacent the mast. Each mast must be leveled using adjusting screws on the ends of the legs prior to finishing erection. Since the adjusting screws have limited movement, the use of this scaffolding system is generally limited to substantially level ground. Safety rails are provided but are loosely held in sockets at the extents of horizontal staging, the horizontal staging affixed to a sleeve sliding upon the mast. The scaffolding system must be anchored to the wall being erected at heights above twelve feet.